Inattentional blindness or selective attention is a psychological phenomenon where people fail to notice things that are going on right under their own noses, because their attention is somewhere else. And sometimes the things that they fail to notice can be quite incredible. The first study of this was conducted in the 1970s by a psychologist named Ulric Neisser. The participants in this study watched a video of six people – three wearing black T-shirts, three wearing white T-shirts – passing a ball around a basketball court and they were asked to count the number of passes made by the white team. A few seconds after the start of the video, a woman with an umbrella strolls casually across the screen, right through the middle of the game. The participants were so caught up in their task that most failed to notice the woman entirely, and even when they were asked directly “did anything strange happen?”, “did anyone else come onto the court” said no. It’s quite hard to imagine this just from hearing about it, but if you google the video, you’ll see how easy it is to miss the woman when you’re focussed on counting the number of passes.
And more recently, two psychologists Christopher Chabris and Daniel Simons decided to push this even further. They started out just trying to replicate Neisser’s original study with a better-quality video, but they had some tape and some time left at the end of the original and decided to see how far they could push it. They ended up having a gorilla walk into the basketball game, stop right in the middle, and stand there thumping his chest, but even so most people didn’t notice. Even though he was there in total for a full 9 seconds. More worryingly, another study found that when doctors were asked to scrutinize an X-ray for signs of cancer, 83% of them failed to notice when a picture of a gorilla had been superimposed on the picture!
Many of you will have probably heard of the invisible gorilla. Chabris and Simons wrote a book with that name, and the UK Psychologist Richard Wiseman wrote another called “Did you spot the Gorilla”. But you might not have thought through the implications for your site. If visitors are very focussed on a particular task – especially if it’s something that requires concentration like typing in their details – they are going to be almost blind to things happening elsewhere on the page. So, if you’re going to have banners, or other products or whatever appear, you need to make sure they do so at a time and place that’s appropriate, not when your visitors’ attention is elsewhere. Eyetracking, creating heatmaps of where your visitors are looking and when, is a great way of checking if they’re focussing on what they should be; or whether the most important parts of your site will pass by as unnoticed as that invisible gorilla.